Was I the only one to think that River Song is the reincarnation of the Master? Maybe it was just the talk of them being at the end of the universe together. The only people there with the Doctor (who escaped alive) were Jack, Martha and the Master. But there was a feminine hand picking up the Master's ring, and the Master would probably know the Doctor's actual name.
Of course that doesn't explain all the affectionate ways...maybe he forgets again who he was? LOL!
*smokes some more of RTD's crack* ;)